This invention relates to methods and apparatus for producing armatures for dynamo-electric machines such as electric motors and generators, and more particularly to improving the balance of such armatures.
The principal components of a dynamo-electric machine armature are typically a shaft, an axially slotted lamination stack or core mounted concentrically on the shaft, a commutator also mounted concentrically on the shaft, insulating end fibers at respective opposite axial ends of the lamination stack, insulating papers in the slots in the lamination stack, coils of wire wound on the lamination stack chiefly by passing through the slots in the stack with coil lead wires extending to the commutator, and a resin coating applied to at least the axial ends of the coils to help stabilize the coils.
It is becoming increasingly important for such armatures to be well balanced about the central longitudinal axis of the armature shaft. This increased importance is due, for example, to a growing interest (on the part of motor manufacturers and users) in motors that operate more smoothly, more reliably, with longer lives, and at higher speeds. The traditional techniques for balancing armatures include subjecting the annular outer surface of the lamination stack to a turning operation to ensure concentricity of that surface with the shaft, milling one or more axial grooves in the outer surface of the lamination stack to remove material from the side of the armature found to be heavier, and/or adding extra resin to the coil ends on the side of the armature found to be lighter. It would be desirable, however, to assemble the armature in such a way that unbalance is eliminated or at least substantially reduced so that the required extent of the above-mentioned traditional balancing operations can be at least substantially reduced. For example, removal of large amounts of material from the outer surface of the lamination stack by annular turning or axial milling may reduce the efficiency of the resulting motor. Also, to the extent that different amounts of material must be removed from different armatures, these techniques are not consistent with producing motors having uniform operating characteristics.
In view of the foregoing, it is an object of this invention to provide dynamo-electric machine armatures with improved balance.
It is a more particular object of this invention to provide methods for assembling dynamo-electric machine armatures in such a way that their balance is improved prior to the manufacturing stage in which final balancing operations are traditionally performed so that the extent to which such traditional final balancing operations must be carried out is at least substantially reduced.